Edma Tcdn Status Monitoring - Freescale Semiconductor MCF52277 Reference Manual

(0x1234567x) retain their original value. In this example the source address is set to 0x12345670, the
offset is set to 4 bytes and the MOD field is set to 4, allowing for a 2
17.8.5

eDMA TCDn Status Monitoring

17.8.5.1 Minor Loop Complete
There are two methods to test for minor loop completion when using software initiated service requests.
The first is to read the TCDn_CITER field and test for a change. (Another method may be extracted from
the sequence shown below). The second method is to test the TCDn_CSR[START] bit and the
TCDn_CSR[ACTIVE] bit. The minor-loop-complete condition is indicated by both bits reading zero after
the TCDn_CSR[START] was set. Polling the TCDn_CSR[ACTIVE] bit may be inconclusive, because the
active status may be missed if the channel execution is short in duration.
The TCD status bits execute the following sequence for a software activated channel:
START
1 1
2 0
3a 0
3b 0
The best method to test for minor-loop completion when using hardware (peripheral) initiated service
requests is to read the TCDn_CITER field and test for a change. The hardware request and acknowledge
handshakes signals are not visible in the programmer's model.
The TCD status bits execute the following sequence for a hardware-activated channel:
Freescale Semiconductor
Table 17-34. Modulo Feature Example
Transfer
Number
1
2
3
4
5
6
TCDn_CSR bits
ACTIVE DONE
0 0
1 0
0 0
0 1
MCF52277 Reference Manual, Rev. 1
Enhanced Direct Memory Access (eDMA)
4
byte (16-byte) size queue.
Address
0x12345670
0x12345674
0x12345678
0x1234567C
0x12345670
0x12345674
State
Channel service request via software
Channel is executing
Channel has completed the minor loop and is idle
Channel has completed the major loop and is idle
17-35